Vulnerability Description
jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. Prior to 4.5.7, JupyterLab's HTML sanitizer allowlists data-commandlinker-command and data-commandlinker-args on button elements, while CommandLinker listens for all click events on document.body and executes the named command without checking whether the element came from trusted JupyterLab UI. A notebook with a pre-saved HTML cell output containing a deceptive button can trigger arbitrary JupyterLab commands - including arbitrary code execution - on a single user click, without any code being submitted for execution by the user. This vulnerability is fixed in 4.5.7.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Jupyter | Jupyterlab | < 4.5.7 |
| Jupyter | Notebook | >= 7.0.0, < 7.5.6 |
Related Weaknesses (CWE)
References
- https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-mqcg-5x36-vfcgMitigationVendor Advisory
- https://access.redhat.com/errata/RHSA-2026:43038
- https://access.redhat.com/security/cve/CVE-2026-42557
- https://bugzilla.redhat.com/show_bug.cgi?id=2477086
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42557.json
FAQ
What is CVE-2026-42557?
CVE-2026-42557 is a vulnerability with a CVSS score of 9.6 (CRITICAL). jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. Prior to 4.5.7, JupyterLab's HTML sanitizer allowlists data-commandlinke...
How severe is CVE-2026-42557?
CVE-2026-42557 has been rated CRITICAL with a CVSS base score of 9.6/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-42557?
Check the references section above for vendor advisories and patch information. Affected products include: Jupyter Jupyterlab, Jupyter Notebook.